The recent technology allows image data to be shared among a plurality of remotely located sites to facilitate communication among the plurality of sites. For example, an image capturing device such as a video camera, an image processing apparatus, and a projection device may be provided at each site. The image capturing device at a first site captures an image of a whiteboard surface at its own site. The image processing apparatus obtains a drawing image drawn by a user onto the whiteboard from the captured image, and transmits the drawing image to the other site for projection onto a whiteboard at the other site, thus allowing the drawing image of each site to be shared among the plurality of sites, for example, as described in U.S. Pat. No. 7,496,229.
The above-described technology of exchanging the drawing images among different sites tends to have low frame rates. More specifically, after the projection device projects the image received from the other site onto the whiteboard, the image processing apparatus usually waits for a few hundred milliseconds before it instructs the image capturing device to capture the image from the whiteboard for further processing. While this results in higher stability of the captured image, it creates another problem as waiting for a predetermined time period before capturing tends to reduce an overall number of images to be transmitted to the other site for a predetermined time period, thus making difficult to obtain higher frame rates.